The purpose of this proposal is to apply current day methodology to study problems of mineral and bone metabolism in newborn infants and children. The methodology to be used includes radioimmunoassay and receptor-binding assays to determine circulating levels of parathyroid hormone, calcitonin, vitamin D, and vitamin D metabolites. Computed tomography will be used to evaluate bone mass. We will continue studies of mineral metabolism in the newborn period with an emphasis on elucidating factors involved in the pathogenesis of neonatal hypocalcemia. Studies are proposed to further our understanding of rickets and osteopenia observed in premature low birth weight infants and to design measures to prevent this disorder. We plan to study the problem of osteopenia in patients with juvenile onset diabetes in an effort to gain insight into factors involved in its pathogenesis. We plan to investigate alterations of bone and mineral metabolism in patients with cystic fibrosis of the pancreas and to evaluate measures to prevent and treat this complication. We will make sequential studies in patients with idiopathic juvenile osteoporosis in an effort to gain knowledge of the pathophysiology of osteoporosis in this disorder. In studies in experimental animals we plan to determine the effect of the "rachitogenic factor" present in soy-protein on vitamin D metabolism.